The present invention relates to ink jet printers and, more particularly, to a printer configuration which provides simple, accurate assembly and alignment of printer component elements. Ink jet printers of the type to which the present invention is directed generally comprise an orifice plate for forming one or more rows of liquid jets and a charge electrode plate provided with a series of charge electrode openings, aligned with the jets, for selectively charging fluid drops formed by the jets during formation of the drops. Such a printer also typically includes a deflection electrode arrangement for deflecting drops charged by the charge rings, and a catcher arrangement for catching drops which are so deflected. Non-deflected drops are deposited upon a moving print medium which is transported below the printer.
Ink jet printers of the above described type are inherently capable of high speed, high resolution printing, but have required close tolerance manufacture of printer elements and precise assembly of these elements. After use of such a printer for a substantial period of time, erosion of the orifice plate may occur and contaminants may be deposited in the fluid supply system. Accordingly, it may be necessary to disassemble the printer periodically for refurbishing the fluid supply system and thereafter reassembling the printer with the charge electrode apertures in precise alignment with the jet forming orifices in the orifice plate. Additionally, the deflection electrode arrangement and the catcher configuration may need to be cleaned or refurbished from time to time and these printer elements must thereafter be realigned precisely with the other elements of the printer. In the past, this has been a somewhat tedious process which is difficult for unskilled or semi-skilled operating personnel in a normal printing environment.
A typical printer arrangement is shown in U.S. Pat. No. 3,701,998, issued Oct. 31, 1972, to Mathis. The Mathis patent discloses a print head providing two rows of jets which is capable of solid print coverage across a print receiving web. Since the Mathis printer contemplates an extremely large number of very small diameter jets, providing a high level of resolution, accurate alignment between the orifice plate and the charge electrode plate in such a printer is critical.
In order to facilitate assembly and disassembly of jet drop printing elements of the type shown in the Mathis patent, U.S. Pat. No. 3,805,273, issued Apr. 16, 1974, to Brady et al. provided an improved mounting arrangement in which the fluidic elements, incorporated into an upper assembly, are segregated from the electrical elements, incorporated into a lower assembly. Such an arrangement provides for relatively easy disassembly of the printer to permit refurbishment of the printer elements. Reassembly of the Brady et al printer, however, is somewhat tedious because of the above mentioned requirement for precise alignment between the orifice plate and the charge ring plate.
U.S. Pat. No. 4,081,804, issued Mar. 28, 1978, to Van Breemen et al., discloses an ink jet printer having an upper assembly and a lower assembly with the orifice plate forming a part of the upper assembly and the charge electrode plate forming a part of the lower assembly. The lower assembly is adapted for mating with the upper assembly in a manner which facilitates alignment of the assemblies. Three precision steel balls are embedded in the charge electrode plate and are engaged by three corresponding rests extending downward from the upper assembly. The three rests respectively have conically-shaped, V-shaped, and flat surfaces for engaging the steel balls. The deflection electrode of the printer is mounted on the upper assembly, while the catcher structures are pivotally mounted on the support structure which also supports the charge electrode plate. While facilitating assembly and alignment of the printer elements, the arrangement of Van Breemen et al requires careful adjustment of the upper assembly rests and the other printer elements. Such adjustments are made more difficult by the fact that the printer elements are not dimensionally referenced from a single printer element structure.
Accordingly, it is seen that there is a need for a simple, easily assembled and aligned, ink jet printer in which the printer elements are aligned upon assembly without substantial adjustment difficulty and in which the printer elements are dimensionally referenced from a single printer element.